Apparatus for bending and tempering glass

ABSTRACT

Sheet glass is heated during conveyance on a conveyor within a furnace. A vacuum holder is positioned within the furnace housing above the conveyor and has a downwardly facing surface with spaced openings in which a vacuum is drawn to receive a glass sheet from the conveyor and support the sheet above the conveyor. The holder surface is disclosed as being both planar and curved and as having a porous cover of ceramic fibers so as to distribute the vacuum and prevent marring of the glass as it is supported. Auxiliary lifters positioned between the rolls or vertical movement of the vacuum holder facilitates glass pickup. A carrier mold ring moves under the supported glass and the vacuum is then terminated so the glass drops onto the ring and bends under the bias of gravity in a manner that allows thin glass to be accurately bent. Subsequently the mold ring is moved from the furnace to a quench unit that temper the bent glass.

This is a continuation, of application Ser. No. 872,201, filed Jan. 25,1978 now abandoned.

TECHNICAL FIELD

This invention relates to apparatus for bending and tempering sheetglass.

BACKGROUND ART

Bent and tempered glass is used extensively for vehicle side and rearwindows to provide good resistance to breakage as well as anaesthetically appealing shape that complements the design of thevehicle. In order to perform the bending and tempering, sheet glass mustbe heated to its deformation point of about 1200° to 1300° F. and thenbent to the required shape before being rapidly cooled by an air sprayin order to temper the glass. Tempering greatly increases the mechanicalstrength of the glass and its resistance to breakage as well as causingthe glass to break into small relatively dull pieces when broken insteadof into large sharp slivers as is the case with untempered glass.

One manner in which glass is bent and tempered is with press bendershaving shaped surfaces between which heated glass is clamped to shape itprior to being air cooled by a quench unit to provide tempering. U.S.Pat. Nos. 3,454,389; 3,476,542; 3,488,178; 3,600,150; and 3,951,634disclose press bending and tempering apparatus for sheet glass.

Sheet glass is also bent and tempered by heating of planar glass sheetswhile supported on bending molds including movable sections. Prior tosoftening of the glass during heating, the sections of the mold areoriented to accommodate for the glass sheet planarity. Upon softening ofthe glass sheet as it is heated, the mold sections move relative to eachother under the force of gravity acting on the sheet and the moldsections in order to provide bending of the sheet prior to rapid coolingthereof which provides its tempering. Thin glass, i.e. on the order of1/8", cannot be bent by this apparatus since it does not have sufficientweight to actuate the pivoting of the mold sections until the glassbecomes so soft that it overbends. U.S. Pat. Nos. 3,269,822; 3,278,287;3,307,930; and 3,365,285 disclose this type of bending and temperingapparatus.

Heating of glass sheets prior to bending and tempering thereof has alsobeen performed on fluid support beds as the glass is conveyed through afurnace. Normally the support bed is inclined slightly with respect tothe horizontal so that gravity engages an edge of the glass with amovable frame that provides the impetus for glass movement along thebed. There is no contact between the bed and the oppositely facingsurfaces of the glass during the conveyance as the glass is heated. Thislack of contact prevents marring and scratching of the soft surfaces ofthe glass as the glass reaches its deformation temperature. However,there normally is mechanical contact with the glass during the bendingafter the heating in preparation for a cooling quench that tempers theglass in its bent condition. U.S. Pat. Nos. 3,497,340; 3,607,187; and3,607,200 disclose glass bending and tempering apparatus of this typewith a fluid support bed.

Vacuum forming of heated glass sheets is disclosed by U.S. Pat. No.3,778,244 wherein the sheet glass is first heated during conveyancealong a roller hearth conveyor. After heating, a lifter with a curveddownwardly facing surface has a vacuum applied thereto about the surfaceto shape the glass. After shaping against the curved surface of thelifter, the vacuum is terminated to drop the glass onto a mold forconveyance to a waiting operator who removes the glass from the mold.Further vacuum forming of the glass to a curved surface of the mold isalso disclosed.

Other bending and tempering apparatus for sheet glass is disclosed byU.S. Pat. Nos. 2,223,124; 2,348,887; 2,646,647; and 2,085,520.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide improved apparatuscapable of bending and tempering thin sheet glass, i.e. on the order of1/8" thick, at relatively high production rates while providing accuratecontrol of the shape to which the glass is bent.

In carrying out the above object, apparatus of the invention includes afurnace with a housing that defines a heating chamber in which glass isheated during conveyance along a roller hearth conveyor. An upwardlyopening lower housing portion and a fixed roof of the furnace housingcooperate with vertically movable side doors to define the heatingchamber. Lower ends of the doors cooperate with the upper ends of sidewalls on the lower housing portion to define side slots through whichends of elongated conveyor rolls project outwardly from the heatingchamber. Heat seals at the slots limit the loss of heat from the heatingchamber to the environment. Continuous drive loops in the form of eitherchains or solid steel belts support the ends of the conveyor rolls andare slidably driven over external support surfaces extending alongsidethe slots to support and frictionally drive the rolls. Upward movementof the side doors permits access to the furnace heating chamber formaintenance and repair.

A vacuum holder of the apparatus is positioned within the heatingchamber above the conveyor rolls and in one embodiment has a downwardlyfacing planar surface with restricted openings spaced thereover. Avacuum is drawn within the restricted openings to receive the heatedsheet of glass from the conveyor and support the glass above theconveyor in preparation for bending. A greater vacuum is drawn toinitially support the glass, while a lesser vacuum is subsequently drawnso as to support the glass without deforming it at the openings in theholder surface. Marring of the glass against the surface is prevented byproviding it with a porous cover made of ceramic fibers. The porouscover also distributes the vacuum between the holder openings. Auxiliarylifters positioned between the conveyor rolls are movable upwardly tolift the sheet of glass toward the vacuum holder so as to aid in pickingit up off the conveyor. Vertical movement of the vacuum holder is alsoprovided for the same purpose, downward movement of the holder locatingits planar surface in proximity to a heated sheet of glass to be pickedup, and upward movement of the holder lifting the glass upwardly in aspaced relationship to the conveyor rolls.

Sensing of the glass position along the conveyor and operation of alateral locator accurately position the glass on the holder surfacewithout requiring the conveyor to be stopped prior to the holderoperation. One locator disclosed operates during the conveyance upstreamfrom the holder and includes one sensor upstream from the locator andanother sensor between the locator and the holder for sensing thelongitudinal position of the glass. Both sensors are coupled to theconveyor drive mechanism and the vacuum holder to coordinate theiroperation. Another lateral locator disclosed operates after the glasshas been lifted by the anxiliary lifters but before it has beeninitially supported on the holder. A single sensor upstream from thislocator is coupled with the conveyor drive mechanism and the auxiliarylifters as well as the vacuum holder to coordinate their operation.

After the sheet of glass is supported on the vacuum holder, a carriermold preferably in the form of a ring is moved under the glass.Termination of the vacuum then drops the sheet of glass onto the moldring so that the glass sags within the furnace heating chamber under thebias of gravity from its planar condition to a curved shape of the ring.Maintaining the carrier ring within the heating chamber of the furnacefor a predetermined period of time, on the order of one to ten seconds,allows the glass to be bent to the required shape. Only the mold ringhas to be changed to bend different size glass to different shapes dueto the planarity of the holder surface. Such is not the case with pressbenders whose curved surfaces can only bend glass to a single curvature.

It is also possible for the center of the holder surface to be slightlyraised relative to its perimeter, on the order of 1/4" for a 4 footsurface, to reversely bend the glass prior to the gravity bending so asto prevent overbending on the mold ring. To make deep bends, anotherembodiment of the holder has a curved surface against which theauxiliary lifters form the glass. Further bending by gravitysubsequently takes place on the mold ring.

A quench unit of the apparatus is positioned adjacent an end of thefurnace housing in which the vacuum holder is received. Movement of themold ring with the bent glass thereon into the quench unit between upperand lower blastheads thereof provides tempering of the glass. Air flowthrough nozzles of the blastheads cools the heated glass rapidly as thetempering takes place to increase its resistance to breakage.

One embodiment disclosed includes a damper which, after completion ofthe tempering, diverts air flow from the upper blasthead to the lowerblasthead so that the glass sheet is picked up off the mold ring. Themold ring then moves back to the furnace and the air is diverted back tothe upper blasthead to drop the glass onto a delivery conveyor. Glassmovement on the delivery conveyor from between the blastheads deliversthe glass from the quench unit to an operator.

In another embodiment disclosed, the mold ring carries the glass fromthe heating chamber to the quench unit for tempering and then to theoperator who removes the glass. Subsequently, the mold ring is drivenback through the quench unit to the heating chamber ready to beginanother cycle.

The auxiliary lifters preferably are T-shaped, each including an uppercrossbar and a stem that projects downwardly from the crossbar betweenthe conveyor rolls. This T-shaped lifter construction is strong andoperable even when the rolls are closely spaced. Each lifter crossbarincludes a woven ceramic cloth cover that engages a heated sheet ofglass as the lifter moves upwardly to pick the glass off the conveyorrolls.

The objects, features, and advantages of the present invention arereadily apparent from the following description of the best mode forcarrying out the invention taken in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side elevation view showing one embodiment ofglass bending and tempering apparatus constructed according to thepresent invention;

FIG. 2 is a top plan view of the apparatus taken along line 2--2 of FIG.1;

FIG. 3 is a schematic view of a furnace and a quench unit of theapparatus taken along line 3--3 of FIG. 1;

FIG. 4 is a top plan view taken along line 4--4 of FIG. 3 showing acarrier mold in the form of a ring on which heated sheet glass is bentunder gravity;

FIG. 5 is a side view of the carrier ring taken along line 5--5 of FIG.4;

FIG. 6 is an enlarged view of a portion of FIG. 4 showing a helicalspring that is wrapped about the carrier ring so as to engage the sheetglass with point contact;

FIG. 7 is a bottom plan view taken along line 7--7 of FIG. 8b showing avacuum holder of the apparatus positioned within the furnace heatingchamber;

FIGS. 8a and 8b are taken in the same direction as FIG. 3 and togethershow a cross-sectional view of the furnace and quench unit of theapparatus;

FIG. 9 is a side elevation view taken along line 9--9 of FIG. 2 showingboth the quench unit and portions of the furnace;

FIG. 10 is a top plan view of the quench unit taken along line 10--10 ofFIGS. 8a and 8b;

FIG. 11 is a side elevation view of auxiliary lifters of the apparatustaken along line 11--11 of FIG. 8b;

FIG. 12 is a top plan schematic view of the apparatus;

FIGS. 13 and 14 are schematic views of other embodiments of apparatusaccording to the present invention;

FIG. 15 is a sectional view taken along line 15--15 of FIG. 14 showing aconveyor roll and lifter construction of the apparatus; and

FIGS. 16 and 17 are schematic elevation views of another embodiment ofthe vacuum holder.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 and 2 of the drawings, one embodiment of the glassbending and tempering apparatus constructed according to the presentinvention is indicated generally by 20 and includes a furnace 22 as wellas a quench unit 24. One end 26 of the furnace 22 receives discretesheets of glass to be bent and tempered while the other end 28 of thefurnace has provisions for bending the glass once it is heated in amanner that is hereinafter described. Quench unit 24 is shown by solidline representation positioned laterally adjacent one side of thefurnace end 28 and receives the heated and bent glass to providetempering thereof in a manner that is likewise hereinafter described. Itis also possible for the quench unit 24 to be positioned at the otherside of the furnace end 28 or at its longitudinal end as shown byphantom line representation. Quench units can also be provided at anytwo or three of these positions to receive heated and bent glass fortempering and thereby increase the system output. The quench unit 24aligned with the longitudinal direction of the furnace can also be usedto temper sheet glass that is not bent.

With reference to FIG. 8b, the furnace 22 in which sheet glass is heatedincludes a housing composed of lower and upper portions 30 and 32,respectively. Lower housing portion 30 is made from refractory blocks 34mounted on a framework of horizontal and vertical beams 36 defining anupwardly opening U shape. A bottom wall 38 of the lower housing portion30 is made from a larger refractory block and includes T-shapedretainers 40 for securing heater elements 42. Side walls 44 of the lowerhousing portion 30 are defined by the refractory blocks 34 extendingupwardly from the bottom wall 38 to support upper refractory end blocks46. Upper housing portion 32 includes a fixed roof 47 and a pair ofvertically movable side doors 48 that extend downwardly from the roof ina U shape to cooperate with the upwardly opening U shape of the lowerhousing portion in defining a heating chamber 50. Fixed roof 47 also hasT-shaped retainers 40 and heater elements 42 secured thereby like thebottom wall 38 of the lower housing portion. A horizontal beam 52 issupported at its opposite ends by vertical beams 54 (only one shown inFIG. 8a) and itself supports horizontal beams 56 that mount nut and boltconnectors 57 for securing the roof 47. A pulley system collectivelyindicated by 58 counterbalances the weight of each door 48 duringmovement thereof between its lower closed position shown by solid linerepresentation and its upper open position shown by phantom linerepresentation. Pulley system 58 includes a counterweight 60 (FIG. 8a)associated with each side door 48 as well as a number of pulleys 62 overwhich cables 64 are trained so that the counterweight moves up and downwith the door upon manual effort applied to the door independently ofthe other door. In the open positions of the side doors, the heatingchamber 50 is accessible for maintenance and repair. In the lower closedpositions, the side doors prevent the escape of heat from the heatingchamber 50.

A conveyor of the apparatus is indicated collectively by referencenumeral 66 in FIG. 8b and includes a plurality of conveyor rolls 68 (seealso FIG. 9) of fused silica particles that are sinter bonded to eachother. Ends of each conveyor roll 68 project outwardly through sideslots 70 defined between the upper end blocks 46 of the lower housingportion and the lower ends 72 of the vertically movable side doors 48.Heat seals 73 on the blocks 46 and lower door ends 72 seal the slots 70to prevent the loss of heat from the furnace to the environment andcooperatively define circular openings (not shown) through which theroll ends project. Continuous drive loops 74 in the form of chains orsolid steel belts are slidably driven over upwardly facing supportsurfaces of members 76 that extend alongside the side slots 70 as bestseen in FIG. 9. Each roll end is positioned between upwardly extendingprojections 78 which have idler rollers 80 (FIG. 8b ) for preventingmovement of the rolls along with the drive loops. Nut and bolt supports82 mount the support surface members 76 on the horizontal beams 36 in avertically adjustable manner to maintain planarity of the upper sides ofall of the rolls 68. Each end of the horizontal beams 36 mounting thesupport surface members 76 rotatably mounts a pulley 84 (FIG. 9) overwhich the associated drive loops 74 are trained. At one end of theconveyor, a cross shaft 85 (FIG. 12) connects the pulleys 84 and a drivemechanism 86 drives these pulleys by a digital drive motor such as theelectric stepper motor 88 which drives a chain 90 to pull the driveloops 74 over the support surfaces and thereby frictionally drive theadjacent roll ends. U.S. Pat. Nos. 3,806,312; 3,934,970; 3,947,242; and3,994,711 disclose this type of frictional roll drive mechanism and theentire disclosure thereof is hereby incorporated by reference.

As seen in FIGS. 3, 7, and 8b, a vacuum platen or holder 92 of theapparatus is positioned within the furnace heating chamber 50 at the endof the furnace adjacent the quench unit 24 and has a downwardly facingplanar surface 94. Vacuum holder 92 is seen in FIG. 8b as including anupper portion 96 of a downwardly opening U shape and a lower portion 98of a relatively thick plate-like construction with edge projections 100received within associated grooves in the upper portion 96 so as to besecured thereto and cooperate therewith in defining a cavity 102. Asheet-like cover 104 made of ceramic fibers, preferably silica, iscompressed in a mat that has a porous construction. Such a silica fibermat is commercially available and, as such, no further descriptionthereof will be given. Any suitable high temperature adhesive is used tosecure cover 104 on the downwardly facing planar surface 94 of the lowerholder portion 98. Aligned openings or holes 106 and 108 through theholder portion 98 and the cover 104 communicate with the cavity 102. Avacuum drawn within the cavity 102 through a duct 110 by a vacuum blower112 (FIG. 3) is thereby drawn in the holes 106 and 108 in order tosupport a heated sheet of glass on the holder above the conveyor rolls68 shown in FIG. 8b. Cover 104 prevents marring or scratching of thesoft glass surface as the glass sheet is engaged with the holder and,due to its porous construction, distributes the vacuum between theholes.

As the glass sheet is conveyed under the vacuum holder 92, a damper 114of duct 110 is located in its solid line indicated position of FIG. 3 byan actuator embodied as a cylinder 116. One end of cylinder 116 ispivotally fixed by a pin 118 to a stationary support while a piston rod119 of the cylinder is secured by a pin 120 to the damper 114. No vacuumreaches the lower holder surface 94 with the damper in this position sothat the glass is free to move under the holder. Once the glass ispositioned under the holder, the cylinder 116 is supplied pressurizedfluid to retract its rod 119 and to move the damper to its positionshown by phantom line representation and indicated at 114'. An opening121 to the environmental atmosphere through duct 110 is open with thedamper in its solid line 114 position and closed by the damper in itsphantom line position 114'. Vacuum is supplied to the lower holdersurface 94 to pick up the sheet of glass with the damper in position114'. Once the heated glass has been picked up by the vacuum holder, thecylinder 116 is supplied pressurized fluid to extend its connecting rod119 and position the damper in the partially open position with respectto duct opening 121 as shown by phantom line representation andindicated by 114". Only a partial vacuum is drawn in the holder by theblower 112 with the damper in this partially opened position as a resultof the atmospheric pressure that can enter the holder openings throughthe duct opening 121. This reduction in the drawn vacuum prevents theheated glass which is softened from being deformed in a dimple-likemanner at the restricted holes or openings 108 that are spaced over theholder surface 94 as best seen in FIG. 7. The vacuum which is drawn inthe partially opened damper position 114" shown in FIG. 3 is about 10%in inches of mercury of the vacuum which is drawn with the damper in itsposition indicated by 114' where the duct opening is closed. When thevacuum holder 92 is ready to release the lifted sheet of glass, as ishereinafter described, the cylinder 116 is supplied pressurized fluid toextend its piston rod 119 in order to locate the damper 114 in its solidline indicated position so that the vacuum drawn at the lower holdersurface 94 is terminated in order to let the glass drop under the forceof gravity.

In connection with the operation of the vacuum holder, reference shouldbe made to the U.S. patent application Ser. No. 872,202, filed Jan. 25,1978 and now abandoned, of Harold A. McMaster and John Stephen Nitschkewhich was filed concurrently with the patent application hereof and ishereby incorporated by reference, application Ser. No. 872,202 havingbeen abandoned by filing on Dec. 11, 1978 of a continuation-in-partapplication Ser. No. 968,231 which issued on May 13, 1980 as U.S. Pat.No. 4,202,681.

Two modes of operation are provided for facilitating the vacuum holderpickup of sheet glass from the conveyor. As seen in FIG. 8b, vacuumholder 92 is supported below the housing roof 47 by vertical rods 122whose lower ends are threaded to receive nuts 123. Holes 124 in the roof47 receive intermediate portions of the rods 122 to allow verticalmovement thereof and upper ends of the rods are interconnected by a bar126 and secured to cables 128 of a pulley system 130. Brackets 132rotatably support pulleys 134 of this system on the horizontal beam 52shown in both FIGS. 8a and 8b and the cables 128 are trained over thesepulleys. As seen in FIG. 8a, a common plate 136 of a cylinder actuator138 is connected to the cables 128. Actuator 138 includes a cylinder 140mounted on the vertical beam 54 and having a piston connecting rod 142connected to the plate 136 by a pin 144. Guide 146 is mounted by abracket on the vertical beam 54 and guides the rod 142 during upward anddownward extending movement by the cylinder 140 upon being supplied asuitable pressurized fluid. Upward movement of the rod 142 allows thecables 128 to lower the holder 92 shown in FIG. 8b toward the conveyorrolls 68 in order to facilitate pickup of the glass by a vacuum suppliedin the manner previously discussed. After the pickup, the vacuum holder92 is raised by downward movement of the rod 142 shown in FIG. 8a so asto move the supported sheet of glass on the holder upwardly away fromthe conveyor.

Auxiliary lifters 148 shown in FIG. 11 are positioned between theconveyor rolls 68 and provide another mode of operation for facilitatingthe vacuum sheet glass pickup by the holder 92. Auxiliary lifters 148have T-shaped cross sections and extend parallel to the conveyor rolls68 and transversely with respect to the direction of sheet glassconveyance within the furnace. Opposite ends of the lifters 148 extendoutwardly through the furnace housing side slots and are supported byelongated bars 150 at the sides of the furnace, these bars being notchedto receive the lower ends of the lifters. A pair of cylinders 152mounted on the vertical beams 36 as shown in FIG. 8b have connectingrods 154 with upper ends connected to the bar 150 by pins 155 seen byreference back to FIG. 11. Pressurized fluid is supplied to cylinders152 in order to extend their rods 154 and raise the associated bar 150as well as the auxiliary lifters 148 from the solid line indicatedposition of FIG. 11 to its phantom line indicated position in order tolift the heated sheet of glass upwardly toward the vacuum holder 92.This upward movement of the glass positions it in proximity to the lowersurface 94 of the vacuum holder so as to facilitate the glass pickup.After the vacuum holder is supporting the glass, cylinders 152 aresupplied pressurized fluid to retract their piston connecting rods 154so as to lower the auxiliary lifters 148 back between the conveyor rolls68.

Rather than using a pair of cylinders for moving each bar 150, it ispossible to use a single cylinder and interconnected linkages operatedby the cylinder. Such a single cylinder linkage support of the auxiliarylifter bars 150 ensures coordinated movement of the bars.

As seen by combined reference to FIGS. 8a, 8b, and 10, spaced rails 156of the quench unit 24 mount a pair of carriers 158 and 160 for movementperpendicular to the direction of glass conveyance within the furnace.Carrier 158 includes crossing straps 162 (FIG. 10) on which a mold inthe form of a carrier ring 164 (hereinafter more fully described) issupported for movement between the furnace 22 and the quench unit 24.Carrier 160 likewise includes crossing straps 166 on which a deliveryring 168 is supported for movement between the quench unit and anoperator who stands adjacent the apparatus at the left-hand side of FIG.8a. Carrier 158 extends into the furnace heating chamber in acantilevered manner upon movement to the right to position ring 164below the vacuum holder 92. In this position, the carrier extendsthrough the housing side slot 70 at the adjacent side of the furnace.Movement of the carrier 158 to the left pulls the ring 164 out of thefurnace through this side slot 70 and moves it into the quench unit 24.

During use, carrier 158 shown in FIG. 10 moves the mold ring 164 beneaththe vacuum holder 92 with a heated sheet of glass supported on its lowerplanar surface 94. Vacuum supplied to the holder 92 is then terminatedso that the heated glass drops down onto the mold ring 164 within thefurnace heating chamber 50. A helical spring 170, see FIGS. 4-6, iswrapped about ring 164 in a helical shape and engages the periphery ofthe glass with point contact so as to minimize any cooling effect thatthe ring will have on the glass. Due to its heated condition, the planarsheet of glass begins to sag under the bias of gravity so as to assumethe curved shape of the ring as seen in FIG. 5. Carrier 158 continues toposition the mold ring 164 within the heating chamber for a momentarydwell period so that the glass sags a sufficient extent withoutoversagging, this period of time depending upon the particularconfiguration to which the glass is to be bent. After this dwell withinthe furnace, normally for one to ten seconds, the carrier 158 moves fromthe furnace heating chamber 50 shown in FIG. 8b to the quench unit 24shown in FIG. 8a and positions the bent sheet of glass between lower andupper blastheads 172 and 174 of the quench unit. Each of theseblastheads is preferably of the type disclosed in U.S. Pat. No.3,936,291, the entire disclosure of which is hereby incorporated byreference.

A blower 176 shown in FIGS. 3 and 9 supplies a duct 178 with air thatacts as a cooling fluid. Branch ducts 180 and 182 from duct 178respectively feed the lower and upper blastheads 172 and 174 so that theair is sprayed from the blastheads through nozzles thereof onto theopposite surfaces of the bent glass carried by the mold ring 164. Thisair supply rapidly cools the glass surfaces to temper the glass andthereby increases its mechanical strength as well as causing the glassto break into small dull pieces. Carrier 158 preferably oscillates backand forth between the blastheads to uniformly distribute the impingementof cooling air with the glass. An actuator in the form of a cylinder 184is then supplied pressurized fluid to extend its piston connecting rod186 and to move the damper 188 of duct 182 from the solid line positionto the phantom line position shown in FIG. 3. This damper movementcloses the branch 182 to the air flow from the blower 176 and divertsthe air supply from the upper blasthead 172 through the duct 180. Airthus supplied through the lower blasthead 172 impinges with the lowersurface of the bent and tempered glass sheet and lifts this glass sheetupwardly off of the mold ring 164 into suspended engagement withsuitable bumpers 190 (FIG. 9) on upper blasthead 174 so that the moldring carrier 158 shown in FIG. 10 can move toward the right back intothe furnace ready to pick up another piece of glass for another cycle.Subsequently, the carrier 160 also moves to the right to position itsdelivery ring 168 below the suspended sheet of glass engaged with theupper blasthead.

When the delivery ring 168 shown in FIG. 10 is positioned below theupper blasthead 174 against which the bent and tempered sheet of glassis suspended, the cylinder 184 of FIG. 3 is supplied a pressurized fluidto retract its rod 186 and pivot the damper 188 from its phantom lineclosed position to its solid line open position. Air from the blower 176is then again supplied to the upper blasthead 174 as well as to thelower blasthead 172 so that the lifted sheet of glass drops down ontothe delivery ring. Prior to the next sheet of glass being moved from thefurnace to the quench unit by the carrier 158 shown in FIG. 10, thecarrier 160 moves the delivery ring to the left side of the apparatus asviewed in FIG. 8a where a waiting operator can pick the glass off of thering. Delivery ring 168 thus functions as a delivery conveyor for thetempered glass. Suitable after-cooling blastheads may follow the quenchblastheads and thereafter cool the glass to room temperature beforeconveyance to the operator.

As seen in FIG. 10, actuators for moving the carriers 158 and 160 areembodied as continuous drive chains 192 and 194, respectively. Drivechains 192 are located at the opposite sides of the quench unit andsecured by connectors 196 to the carrier 158. Chain sprockets 198 and200 have the chains 192 trained over them with the sprockets 198interconnected by a hollow cross-shaft sleeve 202 that couples thechains 192 for operation with each other. Likewise, chains 194 aresecured to the carrier 160 by connectors 204 and are trained oversprockets 206 and 208 which are respectively aligned with the sprockets198 and 200. A cross shaft 209 extends through sleeve 202 andinterconnects the sprockets 206 with each other. Drive chains 210 and211 shown in FIG. 10 drive respective sprockets 212 and 213 from digitaldrives such as the electric stepper motors 214 and 215 in order to movethe carriers 158 and 160 by the actuator chains 192 and 194independently of each other. Stepper motor 214 provides rapid movementof the carrier 160 on which the mold ring 164 is thereby moved from thefurnace into the quench unit without significant heat loss. Accuratecontrol of the acceleration and deceleration involved is also possiblewith the stepper motor drive of the carrier ring to prevent the glassfrom being marred by sliding on the ring as it starts and stops.

Reference should be made to the U.S. patent application of Harold A.McMaster and John Stephen Nitschke, Ser. No. 872,128, filed Jan. 25,1978 and now abandoned, which was filed concurrently with the patentapplication hereof and is hereby incorporated by reference, for a morecomplete understanding of the manner in which carrier 158 is drivenbetween the furnace and the quench unit.

The manner in which the vacuum holder picks up the heated glass from theconveyor and maintains the glass planar prior to dropping the glass ontothe mold ring for bending under gravity gives great productionflexibility for bending and tempering glass of different sizes andshapes. Any size and shape of glass can be bent and tempered on theapparatus without changing the vacuum holder due to the planar shape ofits surface 94. Only the shape and size of the mold ring 164 (FIGS. 4-6)must be changed in order to accommodate for bending and tempering ofdifferent size and shape glass sheets. Also, locating the quench unit 24laterally with respect to the direction of glass conveyance through thefurnace 22 from its end 26 to end 28 (see the solid line position of thequench unit in FIG. 2) allows the glass to also pass straight out thefurnace end 28 through a door opening 216 (FIG. 9) where a quench unitfor tempering planar sheet glass can be located. As previouslymentioned, another quench unit can also be located on the opposite sideof the furnace end 28 shown in FIG. 2 from the quench unit 24 so thatglass sheets can be received from the furnace and transferred to thequench units on both sides of the furnace for tempering after firstbeing bent in order to increase production output.

Planar surface 94 of the vacuum holder may have its center slightlyraised with respect to its periphery, i.e. about one quarter of an inchhigher on a surface of a 4 foot dimension so that the surface is notcompletely planar although it is generally planar. Such a slightlyconcave downward but generally planar surface reversely bends the glassprior to the bending on the ring to prevent overbending under the forceof gravity.

With reference to FIG. 12, a control panel 216 of the glass bending andtempering apparatus 20 is coupled to a lateral locator 218 by electricalor hydraulic lines 220 and 220a and b. Locator 218 includes a pair ofcylinders 222a and 222b which have associated piston connecting rods224a and 224b that extend into the housing of furnace 22 through theside slots from which the conveyor rolls 68 project outwardly to bedriven by the continuous drive loops 74. As the sheets of glass G areconveyed from the right to the left over the conveyor rolls, a firstphotoelectric sensor 225 coupled to panel 216 by a line 225' senses theglass to thereby actuate locator cylinders 222a and b so as to extendtheir piston connecting rods 224a and b. Engagement of the rods with thesheets of glass G properly locates the glass at the correct laterallocation on the rolls with respect to the vacuum holder in the properangular orientation. Any improper angularity or lateral positioning ofthe sheets of glass G on the rolls is thus corrected by this locator218. A second photoelectric sensor 226 positioned within the furnace 22and coupled to control panel 216 by a line 228 senses the leading edgeof the located glass sheet G as it is conveyed toward the left past thelocator 218. It will be noted that the glass sheets G are triangular inshape as shown, being designed as control vent windows for vehicles. Twosensors are necessary since the location of the leading glass edge canchange as the glass slides along the rolls during operation of thelocator 218. The exact position of the sheet glass with respect to thevacuum holder 92 is known at all times since the electric motor 88 ofdrive mechanism 86 is coupled by a line 230 to a counter 231 of thecontrol panel 216 as is the sensor 226 by line 228. Control lines 232and 234 connect the vacuum holder cylinder actuator 140 and theauxiliary lifter cylinder actuators 152, respectively, to the controlpanel 216 and counter 231 thereof so that operation of these componentsis coupled with the sensing of the glass position by counting each motorrevolution. Glass can thus be picked up off of the conveyor withoutfirst stopping its movement while always properly locating the glasslongitudinally along the direction of conveyance with respect to themold ring 164 that has a corresponding triangular shape with a requiredcurvature for bending of the glass. The chain actuators 192 and 194 formoving the mold and delivery rings 164 and 168 are also coupled by lines236 and 238 to the control panel 216 in order to coordinate the movementof the sheet glass to the quench unit 24 from the furnace 22 and fromthe quench unit to the operator.

FIG. 13 is a schematic view similar to a portion of FIG. 12 of anotherembodiment of the apparatus. Mold ring 164 is moved by its stepper motordriven chain actuator 192 from the furnace end 28 to and through thequench unit 24 in this embodiment. There is no transfer of the glass toanother delivery ring by diverting air flow to the lower blasthead fromthe upper blasthead as with the previous embodiment of FIGS. 1-12. Afterremoval of the glass from ring 164 by the operator, the ring is drivenback to the furnace ready to begin another cycle.

With both embodiments of the apparatus, the mold ring 164 is preferablyreciprocated by its carrier drive within the quench unit 24 todistribute the flow of air sprayed onto the glass. This distributionprovides uniformity to the tempering of the glass.

A modified version of the apparatus is shown in FIG. 14 and indicated by20'. Except as will be noted, many of the components of this modifiedapparatus are the same as the previously described apparatus and as suchbear like reference numerals. However, the locator 218 is locatedadjacent the vacuum holder 92 rather than upstream from the singlesensor 226. The longitudinal position of the sheet of glass G is sensedby sensor 226 to control operation of the vacuum holder 92. Aftercylinders 152 raise the bars 150 and the auxiliary lifters 148, thesheet of glass G supported on the auxiliary lifters is engaged byextension of the rods 224a and b of the locator cylinders 222a and b andslid along the auxiliary lifters to the proper angular orientation andlateral position. Vacuum subsequently supplied to the holder 92 in thesame manner previously described then engages the sheet of glass withits downwardly facing lower surface so that the auxiliary lifters cansubsequently be lowered prior to the mold ring moving under the vacuumholder. Control panel 216 and its counter 231 coupled to the electricmotor 88, the vacuum holder cylinders 140 and 152, the locator 218, andthe sensor 226 provide sequenced operation of the apparatus.

Auxiliary lifters 148 each have the T shape shown in FIG. 15 and includean upper crossbar 236 and a lower stem 238 that projects downwardly fromthe crossbar. This T shape provides a rigid auxiliary lifter than can bepositioned between the conveyor rolls 68, even when the rolls areclosely spaced, and nevertheless function as required. Crossbar 236 canhave a width greater than the spacing between the rolls 68 and still belocated below the upper sides of the rolls in the lower position so thatthe glass G can be conveyed on the rolls prior to being picked up asshown by the phantom line indicated position. A cover 240 of wovenceramic cloth, i.e. fiber glass cloth, over the upper side of thecrossbar 236 is secured by clips 242 and engages the glass G as it ispicked up and slid along the auxiliary lifter by the locator 218previously described in connection with FIG. 14. Two L-shaped steelmembers 244 are secured to each other in a suitable manner such as bywelding or rivets to provide the T shape of the lifter 148. Of course,it is also possible to utilize a unitary member of a T shape to providethe auxiliary lifter. Likewise, it is possible for the cover 240 to havea tubular shape through which the auxiliary lifter stems rather thanproviding the securement clips 242.

With reference to FIGS. 16 and 17, a modified embodiment 92' of thevacuum holder is shown as having a downwardly facing surface 94' whichis of a curved shape. A heated sheet of glass is conveyed under thevacuum holder 92' by the conveyor 66 and then lifted upwardly by theauxiliary lifters 148 which move from the solid line position of FIG. 16to the phantom line position thereof to engage the sheet of glass G asshown against the curved surface 94'. Ends of the auxiliary lifters 148are supported by a suitable power-operated actuator which is capable oflifting auxiliary lifters at the left and right extremes a greaterdistance than the ones in the center to conform the sheet of glass withthe downwardly convexed shape of the curved surface on the vacuumholder. A vacuum drawn within the holder 92' then supports the sheet ofglass against the surface 94' and the auxiliary lifters 148 are moveddownwardly. Carrier 158 then moves the mold ring 164' beneath the holder92' and the vacuum being drawn is terminated so that the sheet of glassG drops onto the mold ring. It will be noted that the mold ring 164' hasa greater curvature than the vacuum holder surface 94'. Further bendingof the sheet of glass G thus takes place on the mold ring 164' under thebias of gravity. Carrier 158 then moves the mold ring 164' from belowthe vacuum holder 92' out of the furnace heating chamber and into thequench unit in the same manner previously described.

Relatively deep bends can be made by the prebending on the holdersurface and the subsequent gravity bending on the ring as described inconnection with FIGS. 16 and 17.

While the best mode for practicing the invention has herein beendescribed in detail, those skilled in this art will recognize variousalternative designs and embodiments for practicing the present inventionas defined by the following claims.

What is claimed is:
 1. Apparatus for bending and tempering glass sheetscomprising: a heating chamber for heating glass sheets to a sufficientlyhigh temperature to permit tempering thereof; a conveyor for conveyingglass sheets through the heating chamber; a holder for receiving aheated glass sheet from the conveyor; said holder having a downwardlyfacing surface of a predetermined shape against which a differential gaspressure supports the heated sheet of glass received from the conveyorin preparation for bending; a mold having a generally open center and acurved shape over at least a substantial portion thereof with a greatercurvature than said predetermined shape of the holder surface; means forproviding relative movement between the mold and the holder such thatthe mold is positioned below the holder to receive the heated glasssheet at tempering temperature from the holder for substantial sagbending of the glass sheet on the mold solely under gravity; a quenchunit for tempering bent glass sheets; and an actuator for moving themold from the holder to the quench unit in a time to control the extentof bending before tempering of the glass sheet.
 2. Apparatus as in claim1 wherein the holder is located within the heating chamber to receivethe heated glass sheet from the conveyor.
 3. Apparatus as in claim 1 or2 wherein the holder surface includes spaced openings at which a vacuumis drawn in order to effect the differential gas pressure that supportsthe heated glass sheet against the holder.
 4. Apparatus as in claim 3wherein the holder has a porous construction at the surface thereof soas to prevent marring or scratching of the heated glass sheet uponengagement thereof with the holder and so as to also distribute thevacuum between the spaced openings.
 5. Apparatus as in claim 3 whereinthe holder includes a cover made of ceramic fibers.
 6. Apparatus as inclaim 1 wherein the holder is positioned above the conveyor and furtherincluding a support for raising and lowering the holder relative to theconveyor, the support lowering the holder to facilitate lifting of theheated glass sheet upwardly off the conveyor and against the downwardlyfacing holder surface in preparation for the bending, and the supportraising the holder such that the mold can move under the holder toreceive the heated glass sheet therefrom for bending.
 7. Apparatus as inclaim 1 wherein the holder is positioned above the conveyor, theconveyor including horizontally extending rolls and auxiliary liftersmovable upwardly between the rolls to raise the heated sheet of glasstoward the holder and thereby facilitate lifting of the glass sheetagainst the downwardly facing surface of the holder in preparation forthe bending, and the auxiliary lifters being movable downwardly betweenthe rolls to allow the mold to move under the holder to receive theheated glass sheet therefrom for bending.
 8. Apparatus as in claim 1wherein the surface of the holder is planar.
 9. Apparatus as in claim 1wherein the surface of the holder has a curved shape, and means forpre-bending the heated glass sheet on the holder prior to the bendingthereof by gravity on the mold.
 10. Apparatus for bending and temperingglass sheets comprising: a heating chamber for heating glass sheets to asufficiently high temperature to permit tempering thereof; a conveyorfor conveying glass sheets generally horizontally through the heatingchamber; a holder positioned within the heating chamber above theconveyor to receive a heated glass sheet therefrom; said holder having adownwardly facing surface of a predetermined shape against which adifferential gas pressure supports the heated sheet of glass receivedfrom the conveyor in preparation for bending; a mold having a generallyopen center and a curved shape over at least a substantial portionthereof with a greater curvature than said predetermined shape of theholder surface; said mold being movable horizontally to a positionwithin the heating chamber between the holder and the conveyor toreceive the heated glass sheet at tempering temperature from the holderfor substantial sag bending of the glass sheet on the mold solely undergravity; a quench unit for tempering bent glass sheets; and an actuatorfor moving the mold from the heating chamber to the quench unit in atime to control the extent of bending before tempering of the glasssheet.
 11. Apparatus for bending and tempering glass sheets comprising:a heating chamber for heating glass sheets to a sufficiently hightemperature to permit tempering thereof; a conveyor for conveying glasssheets generally horizontally through the heating chamber; a vacuumholder positioned within the heating chamber above the conveyor andhaving a downwardly facing surface of a predetermined shape with spacedopenings at which a vacuum is selectively drawn; a support for loweringand raising the holder; the support lowering the holder toward theconveyor to facilitate pickup of a heated glass sheet therefrom by avacuum drawn at the holder surface openings; the support raising theholder with the glass sheet thereon to support the glass sheet withinthe heating chamber above the conveyor in preparation for bending; amold having a generally open center and a curved shape over at least asubstantial portion thereof with a greater curvature than saidpredetermined shape of the holder surface; said mold being movablehorizontally to a position within the heating chamber between the raisedholder and the conveyor to receive the heated glass sheet at temperingtemperature from the holder for substantial sag bending of the glasssheet on the mold solely under gravity; a quench unit for tempering bentglass sheets; and an actuator for moving the mold from the heatingchamber to the quench unit in a time to control the extent of bendingbefore tempering of the glass sheet.
 12. Apparatus for bending andtempering glass sheets comprising: a heating chamber for heating glasssheets to a sufficiently high temperature to permit tempering thereof; aroller conveyor including horizontally extending rolls for conveyingglass sheets generally horizontally through the heating chamber; aholder positioned within the heating chamber above the conveyor andhaving a downwardly facing surface of a predetermined shape at which avacuum is selectively drawn; auxiliary lifters that are raised andlowered between the rolls below the holder; the auxiliary lifters beingraised to lift a heated glass sheet on the conveyor upwardly toward theholder to facilitate pickup thereof by a vacuum drawn at the holdersurface openings; the auxiliary lifters thereafter being lowered suchthat the holder supports the glass sheet within the heating chamberabove the conveyor in preparation for bending; a mold having a generallyopen center and a curved shape over at least a substantial portionthereof with a greater curvature than said predetermined shape of theholder surface; said mold being movable horizontally to a positionwithin the heating chamber between the holder and the conveyor toreceive the heated glass sheet at tempering temperature from the holderfor substantial sag bending of the glass sheet on the mold solely undergravity; a quench unit for tempering bent glass sheets; and an actuatorfor moving the mold from the heating chamber to the quench unit in atime to control the extent of bending before tempering of the glasssheet.
 13. Apparatus for bending and tempering glass sheets comprising:a heating chamber for heating glass sheets to a sufficiently hightemperature to permit tempering thereof; a conveyor for conveying glasssheets generally horizontally through the heating chamber; a holderpositioned within the heating chamber above the conveyor and having adownwardly facing planar surface with spaced openings at which a vacuumis drawn to support a heated sheet of glass received from the conveyorsuch that the glass sheet is positioned within the heating chamber abovethe conveyor in preparation for bending; a mold having a generally opencenter and a curved shape; said mold being movable horizontally to aposition within the heating chamber between the holder and the conveyorto receive the heated glass sheet from the holder for substantial sagbending of the glass sheet on the mold solely under gravity; a quenchunit for tempering bent glass sheets; and an actuator for moving themold from the heating chamber to the quench unit in a time to controlthe extent of bending before tempering of the glass sheet.
 14. Apparatusfor bending and tempering glass sheets comprising: a heating chamber forheating glass sheets to a sufficiently high temperature to permittempering thereof; a conveyor for conveying glass sheets generallyhorizontally through the heating chamber; a holder positioned within theheating chamber above the conveyor and having a downwardly facingsurface of a curved shape; means for initially bending a heated glasssheet received from the conveyor against the curved surface of theholder and for supporting the glass sheet in contact with the holdersurface in preparation for further bending; a mold having a generallyopen center and a curved shape over at least a substantial portionthereof with a greater curvature than said curved shape of the holdersurface; said mold being movable horizontally to a position within theheating chamber between the holder and the conveyor to receive theheated glass sheet at tempering temperature from the holder for furtherbending of the glass sheet on the mold solely under gravity; a quenchunit for tempering bent glass sheets; and an actuator for moving themold from the heating chamber to the quench unit in a time to controlthe extent of bending before tempering of the glass sheet.
 15. Apparatusfor bending and tempering glass sheets comprising: a heating chamber forheating glass sheets to a sufficiently high temperature to permittempering thereof; a roller conveyor including elongated rolls forconveying glass sheets generally horizontally through the heatingchamber; a pair of continuous drive loops that support and frictionallydrive the conveyor rolls; a pair of spaced support surfaces on which thepair of drive loops are respectively supported and slidably driven; aholder positioned within the heating chamber above the conveyor andhaving a downwardly facing surface of a predetermined shape includingspaced openings at which a vacuum is selectively drawn to support aheated sheet of glass received from the conveyor such that the glasssheet is positioned within the heating chamber above the conveyor inpreparation for bending; a mold having a generally open center and acurved shape over at least a substantial portion thereof with a greatercurvature than said predetermined shape of the holder surface; said moldbeing movable horizontally to a position within the heating chamberbetween the holder and the conveyor to receive the heated glass sheet attempering temperature from the holder for substantial sag bending of theglass sheet on the mold solely under gravity; a quench unit fortempering bent glass sheets; and an actuator for moving the mold fromthe heating chamber to the quench unit in a time to control the extentof bending before tempering of the glass sheet.
 16. Apparatus forbending and tempering glass sheets comprising: a heating chamber forheating glass sheets to a sufficiently high temperature to permittempering thereof; a roller conveyor including elongated rolls forconveying glass sheets generally horizontally through the heatingchamber; a pair of continuous drive loops that support and frictionallydrive the conveyor rolls; a pair of spaced support surfaces on which thepair of drive loops are respectively supported and slidably driven; aholder positioned within the heating chamber above the conveyor andhaving a downwardly facing surface of a predetermined shape includingspaced openings; means for drawing a vacuum within the spaced openingsof the holder so as to support a heated sheet of glass received from theconveyor such that the glass sheet is positioned within the heatingchamber above the conveyor in preparation for bending; said vacuumdrawing means including a control therefor so as to initially draw agreater vacuum to secure the glass sheet to the holder and so as tosubsequently draw a lesser vacuum to maintain the glass sheet supportedwithout deforming the glass sheet at the spaced openings of the holdersurface; a mold having a generally open center and a curved shape overat least a substantial portion thereof with a greater curvature thansaid predetermined shape of the holder surface; said mold being movablehorizontally to a position within the heating chamber between the holderand the conveyor to receive the heated glass sheet at temperingtemperature from the holder for substantial sag bending of the glasssheet on the mold solely under gravity; a quench unit for tempering bentglass sheets; an actuator for moving the mold from the heating chamberto the quench unit in a time to control the extent of bending beforetempering of the glass sheet; means for effecting a differential gaspressure at the upper and lower surfaces of the bent glass sheet on themold to lift the bent glass sheet upwardly off the mold and therebypermit withdrawal of the mold from beneath the lifted glass sheet; and aconveyor for receiving the lifted glass sheet to provide movementthereof for cooling and delivery to an operator.
 17. Apparatus as inclaim 15 or 16 further including a support for raising and lowering thevacuum holder; the support lowering the holder into proximity with therolls of the roller conveyor to facilitate lifting of a heated glasssheet; and the support subsequently raising the holder into a spacedrelationship with the conveyor rolls to permit the mold to move underthe holder to receive the heated glass sheet therefrom for bending. 18.Apparatus as in claim 15 or 16 further including a plurality ofauxiliary lifters movable vertically between the rolls of the conveyorand having elongated shapes extending parallel to the rolls; and meansfor moving the auxiliary lifters upwardly between the rolls to lift aheated glass sheet into proximity with the holder so as to facilitatethe initial vacuum support thereof and for subsequently lowering theauxiliary lifters downwardly between the rolls to allow the mold to moveabove the conveyor rolls and below the holder to receive the glass sheetfrom the holder for bending.